Solid-state light sources such as LDs (Laser Diodes: semiconductor lasers) and LEDs (Light Emitting Diodes) that have a longer service life than conventionally used mercury lamps are increasingly coming into use as the light sources of projectors.
However, a dustproof construction that prevents a decrease in brightness caused by the infiltration and adherence of dust is necessary for achieving long-term maintenance-free operation. As disclosed in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2014-092599), one method employs a circulating cooling construction that encloses the entire light source unit such that there are minimal gaps to realize a sealed space, circulates the internal air by means of a circulation fan, and discharges the internal heat to the outside by means of a heat exchanger composed of a heat-receiving heat sink and a heat-radiating heat sink to suppress any increase in the temperature of the internal air.